1. 1/7/2008 1 後卓越計畫進度報告 Broadband System Laboratory Advisor : Prof. Chin-Liang Wang Presented by Tran Duc Thang A NEW TECHNIQUE FOR LOCALIZATION IN WIRELESS SENSOR NETWORKS

2. 2 RSS-Ratio Technique  The RSS have been popular modeled by a log- normal model: where P i : received power at sensor from beacon i (in dB);

3. 3 RSS-Ratio Technique  Assume that a sensor node can receive signal from 3 beacons - VB1, VB2, VB3. The RSS will be RSS1, RSS2, RSS3. Assume that RSS1 > RSS3 > RSS2.  VB1, VB2, VB3 know their position. The distance between VB1 and VB2 is h, between VB1 and VB3 is s  Step 1: On VB1_VB2, choose the point D 12 which satisfy Similarly, choose D 13 on VB1_VB3  Step 2: From D 12 and D 13, sketch two perpendicular lines d 12, d 13. The intersection of this two lines is the first-estimation position C(x e,y e )..

4. 4 RSS-Ratio Technique C(x e,y e ): x e =x VB1 +s/(a 13 +1); y e =y VB1 +h/(a 12 +1) (a 12 >a 13 ) C(x e,y e ): x e =x VB1 -s/(a 13 -1); y e =y VB1 +h/(a 12 +1) (a 12 <a 13 ) a 12h is the ratio between the distance from first- estimation position and VB2, VB1 a 13h is the ratio between the distance from first- estimation position and VB3, VB1 Clearly that a 12h < a 12org, a 13h < a 13org

5. 5 RSS-Ratio Technique l 12 h-l 12 l 13 s - l 13 VB1 VB2 VB3 h Real position first-estimation position final-estimation position d12 d13 D 12 D 13 Estimation process

6. 6 RSS-Ratio Technique  Step 3: Estimation Process – A half algorithm Define Ac: Accuracy Coefficient (e.g. Ac=0.05) If a 12h < a 12org - Ac  a 12h := a 12h + (a 12org - a 12h )/2 If a 13h < a 12org - Ac  a 13h := a 13h + (a 13org - a 13h )/2 C’(x e,y e ): x e =x VB1 +s/(a 13h +1); y e =y VB1 +h/(a 12h +1) (a 12org >a 13org ) C’(x e,y e ): x e =x VB1 -s/(a 13h -1); y e =y VB1 +h/(a 12h +1) (a 12org <a 13org ) Final-estimation position will have a 12org – a 12h <= Ac a 13org – a 13h <= Ac